Connected: An Internet Encyclopedia
RFC 1866 - 4.2.1. Undeclared Markup Error Handling

Top: Connected: An Internet Encyclopedia
Up: Requests For Comments
Up: RFC 1866
Up: 4. HTML as an Internet Media Type
Up: 4.2. HTML Document Representation
Prev: 4.2. HTML Document Representation
Next: 4.2.2. Conventional Representation of Newlines

### 4.2.1. Undeclared Markup Error Handling

To facilitate experimentation and interoperability between implementations of various versions of HTML, the installed base of HTML user agents supports a superset of the HTML 2.0 language by reducing it to HTML 2.0: markup in the form of a start-tag or end- tag, whose generic identifier is not declared is mapped to nothing during tokenization. Undeclared attributes are treated similarly. The entire attribute specification of an unknown attribute (i.e., the unknown attribute and its value, if any) should be ignored. On the other hand, references to undeclared entities should be treated as data characters.

For example:

        <div class=chapter><h1>foo</h1><p>...</div>
          => <H1>,"foo",</H1>,<P>,"..."
        xxx <P ID=z23> yyy
          => "xxx ",<P>," yyy
        Let &alpha; &amp; &beta; be finite sets.
          => "Let &alpha; & &beta; be finite sets."

Support for notifying the user of such errors is encouraged.

Information providers are warned that this convention is not binding: unspecified behavior may result, as such markup does not conform to this specification.

Next: 4.2.2. Conventional Representation of Newlines

Connected: An Internet Encyclopedia
RFC 1866 - 4.2.1. Undeclared Markup Error Handling